1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly to a method for informing a user of a busy state in the case where a call reception is established with a private mobile communication network subscriber being in a call connection state with a public network in a system for providing public and private mobile communication services at the same time.
2. Description of the Related Art
Typically, a mobile communication network is classified into a public mobile communication network and a private (or office) mobile communication network, but it is impossible to interwork the public mobile communication network and the private mobile communication network. That is, a mobile communication system is designed and implemented to enable only a public mobile communication service or only a private mobile communication service, so that a subscriber of a mobile communication terminal registered in a network can receive a communication service over a specific network with which the subscriber is registered. Therefore, a subscriber of a mobile communication terminal registered in the public mobile communication network cannot receive a private mobile communication service, and a subscriber of a mobile communication terminal registered in a private mobile communication network cannot receive a public mobile communication service.
As a result, it is necessary for a subscriber of a mobile communication terminal to receive a public mobile communication service and a private mobile communication service at the same time, using a single mobile communication terminal. In case of implementing a system for providing public and private mobile communication services at the same time, it is necessary for the system to determine whether a called party's call is a call generated from a public mobile communication network or a call generated from a private mobile communication network.
However, in the case where a mobile communication terminal receiving the public and private mobile communication services at the same time is in a private network and then generates a call origination message, it is possible for a private mobile communication system to recognize a public network call origination or a public network call reception during a message routing procedure, but it is impossible for the private mobile communication system to recognize whether a call connection state expires.
That is, in the case where a call reception is established with a private wireless network subscriber being in a call connection state with a public network, it is impossible to recognize a public network busy state. Likewise, in accordance with a conventional system, a specific message such as a channel allocation/release (allocation and release) message in a call connection state is composed of traffic state packets, and it is impossible for a private wireless system to analyze the specific message.